While thinking about what sorts of maps I needed for my ideas for the Phase Shift mod to play out the way I had in mind, I realized that no current maps really fit the bill. Because I am forcing the player to expand to new mines throughout the entire game, there has to be available to each player a roughly symmetric supply of many reasonably defendable mining positions. Most OP2 maps, however, are anything but symmetric, and very few have well defined base positions beyond the player's start position.
Some other RTSes do have exactly this problem, so I turned to one I played a lot in the past, Starcraft 2, for ideas. The following map is based loosely on Ohana, a 2 player map from that game. The first image is a 128x128 mockup of about what I wanted to put into the map, and the next image is what I've achieved so far. In the mockup, brown squares are common metal mines and orange ones are rare; the size of the square is the number of bars of the mine.
One thing that bothers me is actually the empty areas - although I certainly plan to put in mud cracks and sand rocks and stuff, the actually empty space is kind of obvious that it's the same 4x4 block repeated many times. I'm sure other mappers have dealt with this, so I'll ask - what's a good way to handle empty spaces?
I'm also a bit worried about how the rotationally symmetric lower half of the map will work out, because the OP2 tileset doesn't seem well suited to supporting that kind of thing. In particular, I'm worried about any asymmetry in how microwave and railgun line of fire interacts with 1 tile of cliff versus 2 tiles of cliff. Does anyone know more about how that works? I was always confused in the campaign by where I was and was not able to fire at a high ground guard post.